U.S. patent application number 14/862795 was filed with the patent office on 2016-02-25 for biomimetic polymer for stabilizing wellbore and method for preparation of the same and drilling fluid.
This patent application is currently assigned to CHINA UNIVERSITY OF PETROLEUM (BEIJING). The applicant listed for this patent is China University of Petroleum (Beijing). Invention is credited to Junbin CHEN, Guancheng JIANG, Taotao LUO, Wei OUYANG, Xianzhu WU, Yang XUAN.
Application Number | 20160053156 14/862795 |
Document ID | / |
Family ID | 51958882 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160053156 |
Kind Code |
A1 |
JIANG; Guancheng ; et
al. |
February 25, 2016 |
BIOMIMETIC POLYMER FOR STABILIZING WELLBORE AND METHOD FOR
PREPARATION OF THE SAME AND DRILLING FLUID
Abstract
The present invention provides a biomimetic polymer for
stabilizing wellbore, a method for preparation of the biomimetic
polymer, and a drilling fluid. The polymer contains carboxymethyl
chitosan that serves as a backbone and dopamine-derived groups
grafted on the backbone. The polymer provided in the present
invention can improve the strength of shale in the wellbore, seal
the shale pores and reduce the filter loss of drilling fluid, and
thereby attains an effect of stabilizing the wellbore in shale
formation in drilling process.
Inventors: |
JIANG; Guancheng; (Beijing,
CN) ; XUAN; Yang; (Beijing, CN) ; WU;
Xianzhu; (Chengdu City, CN) ; CHEN; Junbin;
(Chengdu City, CN) ; OUYANG; Wei; (Chengdu City,
CN) ; LUO; Taotao; (Chengdu City, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
China University of Petroleum (Beijing) |
Beijing |
|
CN |
|
|
Assignee: |
CHINA UNIVERSITY OF PETROLEUM
(BEIJING)
Beijing
CN
|
Family ID: |
51958882 |
Appl. No.: |
14/862795 |
Filed: |
September 23, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14611086 |
Jan 30, 2015 |
|
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14862795 |
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Current U.S.
Class: |
507/110 |
Current CPC
Class: |
C08F 8/32 20130101; C08L
51/02 20130101; C08F 8/32 20130101; C08B 37/003 20130101; C09K
8/035 20130101; C08F 251/00 20130101; C08L 5/08 20130101; C08F
251/00 20130101; C08F 251/00 20130101; C08F 220/06 20130101 |
International
Class: |
C09K 8/035 20060101
C09K008/035 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2014 |
CN |
201410062056.X |
Claims
1-5. (canceled)
6. A method for preparation of a polymer containing constitutional
units represented by formula I, comprising: (1) allowing a polymer
containing constitutional units represented by formula III to have
a graft copolymerization reaction with unsaturated carboxylic acid
represented by general formula R.sub.4CH.dbd.CHCOOH; (2) allowing
polymer obtained in (1) to have a condensation reaction with
dopamine and/or dopamine hydrochloride; ##STR00015## wherein, R'
and R'' are H or --CH.sub.2COOR.sub.3' independently, and R' and
R'' are not H at the same time; R.sub.3' is H or an alkali metal;
and R.sub.4 is H or C.sub.1-C.sub.10 alkyl.
7. The method according to claim 6, wherein in (1), conditions of
the graft copolymerization reaction include: reaction temperature
is 50-90.degree. C. and reaction time is 1-10 h; calculated in
hydroxyl in the polymer containing the constitutional units
represented by formula III, the molar ratio of the polymer
containing the constitutional units represented by formula III to
the unsaturated carboxylic acid is 1:0.1-4.
8. The method according to claim 7, wherein conditions of the graft
copolymerization reaction include: reaction temperature is
60-80.degree. C. and reaction time is 2-6 h; calculated in hydroxyl
in the polymer containing the constitutional units represented by
formula Ill, the molar ratio of the polymer containing the
constitutional units represented by formula Ill to the unsaturated
carboxylic acid is 1:0.5-3.
9. The method according to claim 6, wherein the graft
copolymerization reaction proceeds with an initiator in presence,
and the initiator is one or more selected from the group consisting
of ammonium eerie nitrate, potassium persulfate, and ammonium
persulfate.
10. The method according to claim 6, wherein carbon number in the
unsaturated carboxylic acid is 3-11.
11. The method according to claim 10, wherein the carbon number in
the unsaturated carboxylic acid is 3-7.
12. The method according to claim 6, wherein in (2), the conditions
of the condensation reaction include: reaction temperature is
20-40.degree. C. and reaction time is 6-36 h; the molar ratio of
the amount of the polymer prepared in (1) calculated in carboxyl to
the total amount of the dopamine and dopamine hydrochloride
calculated in amido is 1:0.01-0.2.
13. The method according to claim 6, wherein the condensation
reaction proceeds with a catalyst in presence, and the catalyst is
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and/or
N,N'-diisopropyl carbodiimide.
14. A drilling fluid, containing a polymer as a wellbore reinforcer
in part or in whole, and based on the total weight of the drilling
fluid, the content of the polymer is 1-7 wt %; wherein the polymer
contains constitutional units represented by formula I:
##STR00016## wherein, R.sub.1 is H, ##STR00017##
--CH.sub.2COOR.sub.3', ##STR00018## or --CH.sub.2COOR.sub.3,
R.sub.2 is H, ##STR00019## and at least one of R.sub.1 and R.sub.2
is ##STR00020## n is an integer equal to or greater than 1; each
R.sub.5 is H or the dopamine-derived group independently, and at
least one of R.sub.5 is the dopamine-derived group; R.sub.4 is H or
C.sub.1-C.sub.10 alkyl, R''' is H, --CH.sub.2COOR.sub.3' or
--CH.sub.2COOR.sub.3, and R.sub.1 and R''' are not H at the same
time; R.sub.3' is H or an alkali metal; and R.sub.3 is the
dopamine-derived group; wherein the polymer is prepared with a
method comprising: (1) allowing a polymer containing constitutional
units represented by formula III to have a graft copolymerization
reaction with unsaturated caboxylic acid represented by general
formula R.sub.4CH.dbd.CHCOOH; (2) allowing a polymer obtained in
(1) to have a condensation raction with dopamine and/or dopamine
hydrochloride: ##STR00021## Wherein, R' and R'' are H or
--CH.sub.2COOR.sub.3' independently, and R' and R'' are not H at
the same time; R.sub.3' is H or an alkali metal; and R.sub.4 is H
or C.sub.1-C.sub.10 alkyl.
15. The drilling fluid according to claim 14, wherein based on the
total weight of the drilling fluid, the content of the polymer is
3-5 wt %.
16. The drilling fluid according to claim 14, wherein the polymer
contains constitutional units represented by the formula I:
##STR00022## wherein, R.sub.1 is H, ##STR00023##
--CH.sub.2COOR.sub.3', ##STR00024## or --CH.sub.2COOR.sub.3,
R.sub.2 is H, ##STR00025## and at least one of R.sub.1 and R.sub.2
is ##STR00026## n is an integer equal to or greater than 1; each
R.sub.5 is H or the dopamine-derived group independently, and at
least one of R.sub.5 is the dopamine-derived group; R.sub.4 is H or
C.sub.1-C.sub.10 alkyl, R''' is H, --CH.sub.2COOR.sub.3' or
--CH.sub.2COOR.sub.3, and R.sub.1 and R''' are not H at the same
time; R.sub.3' is H or an alkali metal; and R.sub.3 is the
dopamine-derived group.
17. The drilling fluid according to claim 14, wherein the
weight-average molecular weight of the polymer is 50,000
g/mol.about.100,000 g/mol.
18. The drilling fluid according to claim 16, wherein R.sub.4 is
C.sub.2-C.sub.10 alkyl.
19. The drilling fluid according to claim 18, wherein R.sub.4 is
C.sub.2-C.sub.6 alkyl.
20. The drilling fluid according to claim 14, further containing an
additive, which is selected from one or more selected from the
group consisting of filtrate reducer, viscosity improver, viscosity
reducer, weight increaser, coating agent, and lubricant.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The application claims for the priority of the patent
application no. 201410062056.X titled as "Biomimetic Polymer for
Stabilizing Wellbore and Method for Preparation of the Same and
Drilling Fluid" filed on Feb. 24, 2014 with State Intellectual
Property Office of China, the entire content of which is
incorporated here by reference.
FIELD OF THE INVENTION
[0002] The present invention relates a biomimetic polymer for
stabilizing wellbore, a method for preparation of the biomimetic
polymer, and a drilling fluid.
BACKGROUND OF THE INVENTION
[0003] As the demand for oil and gas resources becomes higher
increasingly in the world, more and more deep and ultra-deep wells,
and shale gas well are drilled. Thus, the performance of drilling
fluid treating agents must meet more demanding requirements.
Wherein, the problem of wellbore stability in the well drilling
process has always been a challenge not solved completely yet in
the world, and accidents such as borehole caving, shrinkage, pipe
sticking, and bit balling, etc. resulted from wellbore instability
cause severe economic loss every year in the petroleum
industry.
[0004] 90% wellbore instability accidents in the drilling process
happen in the shale formation, where the dispersion and exfoliation
of shale resulted from hydrated swelling of clay in the shale is
the root chemical factor for wellbore instability. As shale gas
extraction becomes an important strategy in China, it is urgent
task for drilling fluid researchers to ensure that the shale
formation remains stable in the drilling process.
[0005] In the development in the past few decades, oil based
drilling fluids always were an ideal choice for solving the problem
of hydrated swelling of shale. However, as the national
environmental laws become strict increasingly, the application of
oil based drilling fluids is restricted owing to the severe damages
of oil based drilling fluids to the environment. Hence, water-based
drilling fluids with strong shale inhibition property have become a
hot spot in the research again.
[0006] The inhibition property of a drilling fluid usually depends
on the performance of the shale inhibitor in the drilling fluid. At
present, in almost all shale inhibitors, the inhibition mechanism
is realized by weakening the hydrated swelling of clay.
[0007] However, in existing commonly used shale inhibitors, the
hydrated swelling of clay can't be inhibited completely. In
addition, the pressure transfer from the drilling fluid to deep
formation through nano-to-micro-sized pores and micro-fractures in
shale is also a major cause for wellbore instability. At present,
there is no appropriate drilling fluid plugging material that can
effectively plug nano-to-micro-sized pores and micro-fractures.
[0008] Therefore, it is urgent task to seek for a technique that
can be used to stabilize wellbore effectively.
SUMMARY OF THE INVENTION
[0009] To overcome the above-mentioned drawbacks in the prior art,
the present invention provides a polymer that can effectively
stabilize wellbore, a method for preparation of the polymer, and a
drilling fluid that contains the polymer.
[0010] The byssus threads of a mussel can adhere to the rock
surface in the water environment, and dopamine--a special amino
acid derivative contained in byssus protein--is proved to be the
key factor for strong subaqueous adhesion of mussel's byssus
threads. When a mussel secretes byssus protein from its body onto a
seabed rock surface, the dopamine groups in the byssus protein will
have a cross-linking cure reaction with Fe.sup.3+ ions in seawater,
and thereby cohesive byssus threads with strong adhesion are
formed, so that the mussel adheres to the rock surface. Enlightened
by the strong subaqueous adhesion of mussel protein, the inventor
of the present invention has found that a biomimetic polymer
obtained by grafting dopamine to carboxymethyl chitosan can
effectively stabilize wellbore. That could be because the polymer
contacts with wellbore shale and is absorbed to the surface of
shale along with the drilling fluid in the drilling process, and is
cross-linked and cured under the complexing action between the
dopamine groups and the Fe.sup.3+ ions on the surface of shale to
form a layer of polymer film in 100 .mu.m-1 mm thickness (the
thickness increases as the polymer concentration in the drilling
fluid increases), which has strong adhesion. The polymer film not
only can effectively prevent the drilling fluid from infiltrating
into the formation, but also has enough strength to partially
balance off the hydration stress borne on the rock, and thereby
attains an effect of plugging the pores in the shale of wellbore
and improving the strength of the shale. In addition, such a linear
polymer that has a large number of branched chains can effectively
plug capillary channels in bentonite mud cakes, and thereby greatly
reduce the filter loss of drilling fluid.
[0011] In a first aspect, the present invention provides a polymer,
wherein the polymer contains carboxymethyl chitosan that serves as
a backbone and dopamine-derived group grafted on the backbone, and
the dopamine-derived group is represented by the following formula
II:
##STR00001##
[0012] Preferably, the polymer contains constitutional units
represented by the following formula I:
##STR00002##
Wherein, R.sub.1 is H,
##STR00003##
[0013]--CH.sub.2COOR.sub.3',
##STR00004##
[0014] or --CH.sub.2COOR.sub.3, R.sub.2 is H,
##STR00005##
[0015] and at least one of R.sub.1 and R.sub.2 is
##STR00006##
n is an integer equal to or greater than 1; each R.sub.5 is H or
the dopamine-derived group independently, and at least one of
R.sub.5 is the dopamine-derived group; R.sub.4 is H or
C.sub.1-C.sub.10 alkyl, R''' is H, --CH.sub.2COOR.sub.3' or
--CH.sub.2COOR.sub.3, and R.sub.1 and R''' are not H at the same
time; R.sub.3' is H or an alkali metal; and R.sub.3 is the
dopamine-derived group.
[0016] Preferably, the weight-average molecular weight of the
polymer is 50,000 g/mol .about.100,000 g/mol.
[0017] Preferably, R.sub.4 is C.sub.2-C.sub.10 alkyl.
[0018] Preferably, R.sub.4 is C.sub.2-C.sub.6 alkyl.
[0019] In a second aspect, the present invention provides a method
for preparation of a polymer that contains the constitutional units
represented by formula I, comprising: [0020] (1) allowing a polymer
containing the constitutional units represented by formula III to
have a graft copolymerization reaction with unsaturated carboxylic
acid represented by general formula R.sub.4CH.dbd.CHCOOH; [0021]
(2) allowing polymer obtained in step (1) to have a condensation
reaction with dopamine and/or dopamine hydrochloride;
##STR00007##
[0021] wherein, R' and R'' are H or --CH.sub.2COOR.sub.3'
independently, and R' and R'' are not H at the same time; R.sub.3'
is H or an alkali metal; and R.sub.4 is H or C.sub.1-C.sub.10
alkyl.
[0022] Preferably, in step (1), the conditions of the graft
copolymerization reaction include: temperature: reaction
temperature is 50-90.degree. C., preferably 60-80.degree. C.;
reaction time is 1-10 h, preferably 2-6 h; calculated in hydroxyl
in the polymer that contains the constitutional unit represented by
formula III, the mole ratio of the polymer containing the
constitutional units represented by formula III to the unsaturated
carboxylic acid is 1:0.1-4, preferably 1:0.5-3; the graft
copolymerization reaction optionally proceeds with an initiator in
presence, and the initiator is one or more selected from the group
consisting of ammonium ceric nitrate, potassium persulfate, and
ammonium persulfate.
[0023] Preferably, the carbon number in the unsaturated carboxylic
acid is 3-11, preferably 3-7.
[0024] Preferably, in step (2), the conditions of the condensation
reaction include: reaction temperature is 10-50, preferably
20-40.degree. C.; reaction time is 2-48 h, preferably 6-36 h; the
mole ratio of the amount of the polymer prepared in step (1)
calculated in carboxyl to the total amount of the dopamine and
dopamine hydrochloride calculated in amido is 1:0.01-0.2,
preferably 1:0.02-0.1; the condensation reaction optionally
proceeds with a catalyst in presence, and the catalyst is
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and/or
N,N'-diisopropyl carbodiimide.
[0025] In a third aspect, the present invention provides a drilling
fluid, wherein, the drilling fluid contains the polymer disclosed
in the present invention as a wellbore reinforcer in part or in
whole.
[0026] Preferably, based on the total weight of the drilling fluid,
the content of the polymer is 1-7 wt %, preferably 3-5 wt %.
[0027] Preferably, the drilling fluid is a water-based drilling
fluid.
[0028] Preferably, the water-based drilling fluid is one or more
selected from the group consisting of fresh-water drilling fluid,
salt water drilling fluid, potassium chloride-polyglycol drilling
fluid, organic silicon drilling fluid, and cationic drilling
fluid.
[0029] Preferably, the drilling fluid further contains an additive,
which is one or more selected from the group consisting of filtrate
reducer, viscosity improver, viscosity reducer, weight increaser,
coating agent, and lubricant.
[0030] The polymer provided in the present invention can improve
the strength of shale in the wellbore, seal the shale pores and
reduce the filter loss of drilling fluid, and thereby attains an
effect of stabilizing the wellbore in shale formation in a drilling
process.
[0031] Other characteristics and advantages of the present
invention will be further detailed in the embodiments
hereunder.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 provides photos that show the morphology change of
shale debris observed within 1 h and 3 h respectively after the
shale debris are immersed in 3 wt % GBFS-1 water solution;
[0033] FIG. 2 provides a SEM photo that shows the morphology of
shale debris after the shale debris are roll-heated for 16 h in tap
water at 120.degree. C. in a roller heater and then taken out and
dried.
[0034] FIG. 3 provides a SEM photo that shows the morphology of
shale debris after the shale debris are roll-heated for 16 h in 3
wt % GBFS-1 water solution at 120.degree. C. in a roller heater and
then taken out, washed with some clean water, and dried.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0035] Hereunder the embodiments of the present invention will be
detailed. It should be appreciated that the embodiments described
here are only provided to describe and explain the present
invention, but shall not be deemed as constituting any limitation
to the present invention.
[0036] The polymer provided in the present invention contains
carboxymethyl chitosan that serves as a backbone and
dopamine-derived groups grafted on the backbone. The
dopamine-derived groups can be grafted to the carboxymethyl
chitosan in a variety of ways.
[0037] According to a preferred embodiment of the present
invention, the polymer provided in the present invention contains
constitutional units represented by the following formula I:
##STR00008##
wherein, R.sub.1 is H,
##STR00009##
--CH.sub.2COOR.sub.3',
##STR00010##
[0038] or --CH.sub.2COOR.sub.3, R.sub.2 is H,
##STR00011##
[0039] and at least one of R.sub.1 and R.sub.2 is
##STR00012##
n is an integer equal to or greater than 1; each R.sub.5 is H or
the dopamine-derived group independently, and at least one of
R.sub.5 is the dopamine-derived group; R.sub.4 is H or
C.sub.1-C.sub.10 alkyl, R''' is H, --CH.sub.2COOR.sub.3' or
--CH.sub.2COOR.sub.3, and R.sub.1 and R''' are not H at the same
time; R.sub.3' is H or an alkali metal; and R.sub.3 is the
dopamine-derived group.
[0040] In the present invention, the dopamine-derived group is
represented by formula II:
##STR00013##
[0041] The weight-average molecular weight of the polymer is 20,000
g/mol.about.150,000 g/mol, preferably 50,000 g/mol.about.100,000
g/mol.
[0042] R.sub.4 is preferably C.sub.2-C.sub.10 alkyl, more
preferably C.sub.2-C.sub.6 alkyl. Examples of R.sub.4 include, but
are not limited to ethyl, propyl, isopropyl, and butyl.
[0043] The polymer provided in the present invention can be
prepared with a method that comprises the following steps: [0044]
(1) allowing a polymer containing the constitutional units
represented by formula III to have a graft copolymerization
reaction with unsaturated carboxylic acid represented by general
formula R.sub.4CH.dbd.CHCOOH; [0045] (2) allowing polymer obtained
in step (1) to have a condensation reaction with dopamine and/or
dopamine hydrochloride;
##STR00014##
[0045] wherein, R' and R'' are H or --CH.sub.2COOR.sub.3'
independently, and R' and R'' are not H at the same time; R.sub.3'
is H or an alkali metal; and R.sub.4 is H or C.sub.1-C.sub.10
alkyl.
[0046] In step (1), the conditions of the graft copolymerization
reaction can include: reaction temperature is 50-90.degree. C.,
preferably 60-80.degree. C.; reaction time is 1-10 h, preferably
2-6 h; calculated in hydroxyl in the polymer containing the
constitutional units represented by formula III, the mole ratio of
the polymer containing the constitutional units represented by
formula III to the unsaturated carboxylic acid can be 1:0.1-4,
preferably 1:0.5-3; the graft copolymerization reaction can
proceeds with an initiator in presence, and the initiator can be
one or more selected from the group consisting of ammonium ceric
nitrate, potassium persulfate, and ammonium persulfate.
[0047] The polymer containing the constitutional units represented
by formula III is carboxymethyl chitosan. The carboxymethyl
chitosan is mixed and contacts with the unsaturated carboxylic acid
preferably in a form of water solution. The water solution of
carboxymethyl chitosan can be obtained by dissolving carboxymethyl
chitosan (with 10,000 g/mol.about.80,000 g/mol weight-average
molecular weight) in water while stirring (the stirring rate can be
100-500 rpm). The volume of water can be determined appropriately,
as long as the carboxymethyl chitosan can be dissolved completely;
preferably, the weight ratio of carboxymethyl chitosan to water is
1:20-50.
[0048] The unsaturated carboxylic acid can be an unsaturated
monocarboxylic acid with carbon number equal to or greater than 3.
The carbon number in the unsaturated carboxylic acid is preferably
3-11, more preferably 3-7. The examples of the unsaturated
carboxylic acid include, but are not limited to acrylic acid and/or
methacrylic acid.
[0049] In step (2), the conditions of the condensation reaction can
include: reaction temperature is 10-50.degree. C., preferably
20-40.degree. C.; reaction time is 2-48 h, preferably 6-36 h; the
mole ratio of the amount of the polymer prepared in step (1)
calculated in carboxyl to the total amount of the dopamine and
dopamine hydrochloride calculated in amido can be 1:0.01-0.2,
preferably 1:0.02-0.1; the condensation reaction can proceeds with
a catalyst in presence, and the catalyst can be
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and/or
N,N'-diisopropyl carbodiimide.
[0050] The drilling fluid provided in the present invention
contains the polymer provided in the present invention as a
wellbore reinforcer in part or in whole.
[0051] There is no specific restriction on the added amount of the
polymer in the present invention. Even though an effect of
stabilizing the wellbore can be attained as long as the polymer is
added into the drilling fluid, preferably, based on the total
weight of the drilling fluid, the content of the polymer is 1-7 wt
%, in order to attain the object of the present invention in a
better way. More preferably, based on the total weight of the
drilling fluid, the content of the polymer is 3-5 wt %.
[0052] In the present invention, the drilling fluid can be any
drilling fluid well known in the art; preferably, the drilling
fluid is a water-based drilling fluid.
[0053] In the present invention, the water-based drilling fluid is
a multi-phase dispersed system, in which water is the base
constituent, and a variety of additives are added.
[0054] The water-based drilling fluid can be any water-based
drilling fluid well known to the person skilled in the art. For
example, the water-based drilling fluid can be one or more selected
from the group consisting of fresh-water drilling fluid, salt water
drilling fluid, potassium chloride-polyglycol drilling fluid,
organic silicon drilling fluid, and cationic drilling fluid.
Wherein, the water can be any water well known to the person
skilled in the art; for example, it can be one or more selected
from the group consisting of fresh water (tap water), seawater, and
saline water. The potassium chloride-polyglycol drilling fluid can
be any potassium chloride-polyglycol drilling fluid well known to
the person skilled in the art; for example, it can be one or more
selected from the group consisting of potassium
chloride-polyethylene glycol drilling fluid, potassium
chloride-polypropylene glycol drilling fluid, potassium
chloride-ethylene glycol/propylene glycol copolymer drilling fluid,
potassium chloride-polyglycerol drilling fluid, and potassium
chloride-polyethylene glycol. The organic silicon drilling fluid
can be any organic silicon drilling fluid well known to the person
skilled in the art; for example, the organic silicon in the organic
silicon drilling fluid can be one or more selected from the group
consisting of sodium methylsiliconate, potassium methylsiliconate,
and organic silicon potassium humate (OSAM-K). The cationic
drilling fluid can be any cationic drilling fluid well known to the
person skilled in the art; for example, the cations in the cationic
drilling fluid can be one or more selected from the group
consisting of 2,3-epoxypropyl trimethyl ammonium chloride,
3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and cationic
polyacrylamide.
[0055] In the present invention, to obtain a better drilling
effect, a variety of additives well known to the person skilled in
the art can be added into the drilling fluid. For example, the
additives can be one or more selected from the group consisting of
filtrate reducer, viscosity improver, viscosity reducer, weight
increaser, coating agent, and lubricant.
[0056] In the present invention, there is no specific restriction
on the added amount of the additives, which is to say, the added
amount can be determined as required by the person skilled in the
art to attain the expected effect. For example, based on the total
weight of the drilling fluid, the content of the filtrate reducer
can be 0.2-3 wt %, the content of the viscosity improver can be
0.2-1 wt %, the content of the viscosity reducer can be 0.2-1 wt %,
the content of the weight increaser can be 0.2-3 wt %, the content
of the coating agent can be 0.2-1 wt %, and the content of the
lubricant can be 0.1-2 wt %.
[0057] The additives can be additives well known to the person
skilled in the art. For example, the filtrate reducer can be one or
more selected from the group consisting of pregelatinized starch,
carboxymethyl starch, carboxymethyl cellulose, sulfonated phenol
formaldehyde resin, sulfonated lignite resin, hydrolyzed
polyacrylonitrile ammonium salt, and polyanionic cellulose (a
water-soluble cellulose ether derivative prepared from natural
cellulose by chemical modification); the viscosity improver can be
one or more selected from the group consisting of xanthan gum,
xanthan CXC polymer, carboxymethyl starch, methylol cellulose,
hydroxyethyl cellulose, carboxymethyl cellulose, polyanionic
cellulose (a water-soluble cellulose ether derivative prepared from
native cellulose by chemical modification), and synthetic viscosity
improver (partially hydrolyzed polyacrylamide); the viscosity
reducer can be one or more selected from the group consisting of
ferric chromium lignin sulfonate, sodium polyacrylate, sodium
methylsiliconate, and sulfonated styrene-maleic anhydride
copolymer; the weight increaser can be one or more selected from
the group consisting of iron ore powder, calcium carbonate powder,
mixture of barite and hematite, and galenite powder; the coater can
be one or more selected from the group consisting of partially
hydrolyzed polyacrylamide (liquid or powder), cationic
polyacrylamide, and polyaluminium chloride; and the lubricant can
be one or more selected from the group consisting of non-ionic
surfactant, graphite, and polyglycol.
[0058] The drilling fluid provided in the present invention can be
used in a variety of oil and gas wells, such as straight wells,
directional wells, extended reach wells, and horizontal wells,
etc.
[0059] Hereunder the present invention will be further detailed in
some examples.
[0060] It should be noted that fresh water (tap water) is used to
simulate a water-based drilling fluid and the polymer is prepared
into a water solution with tap water in the examples of the present
invention, for the convenience of measuring the effect of the
polymer as a wellbore stabilizer.
[0061] In the following examples and comparative examples:
[0062] The weight-average molecular weight is measured with a gel
permeation chromatograph (Model 2410, Waters Company (USA)),
wherein, the solvent is water, the flow rate is 1 mL/min., and the
test temperature is 40.degree. C.
Example 1
[0063] 1) Load 1,000 kg industrial water into a reactor, add 50 kg
carboxymethyl chitosan (purchased from Beijing DaTianFengTuo
Chemical Technology Co., Ltd., with a structure represented by
formula III, weight-average molecular weight is 52,000 g/mol,
substitution degree of carboxymethyl is 1.4, the same below) while
stirring; continue stirring after the materials are added, till the
carboxymethyl chitosan is dissolved completely and there is no
flocculated solid suspension in the solution essentially. [0064] 2)
Add 50 kg acrylic acid into the water solution of carboxymethyl
chitosan, stir for 5 minutes, and then add 2 kg nitric acid and
continue stirring, till the carboxymethyl chitosan, acrylic acid,
and nitric acid are mixed homogeneously in the solution; next, add
4 kg ammonium ceric nitrate, and stir till the ammonium ceric
nitrate is dissolved completely. Then, heat up the reaction system
to 70.degree. C., start timing once the temperature in the reactor
reaches 70.degree. C., and let the reaction to proceed for 4 h.
Then, cool down the reactor to 25.degree. C. The product in the
first stage is a straw yellow clear liquid. [0065] 3) Add 5 kg
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in the
cooled reaction system (split 5 kg
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride into 5
portions, stir for 15 minutes after a portion is added, and then
add the next portion, till all of the portions are added). Then,
stir for 10-16 h at room temperature, till the
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is
dissolved completely. The product is still a straw yellow clear
solution. [0066] 4) Add 5 kg dopamine hydrochloride into the system
that contains dissolved
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, keep
the reaction for 24 h at room temperature while stirring, till a
final reaction product GBFS-1 is generated. The final reaction
product is a pale brown clear liquid with certain viscosity. The
measured weight-average molecular weight of the reaction product
GBFS-1 is 84,320 g/mol.
Example 2
[0067] Prepare a polymer GBFS-2 with the same method as that used
in example 1, wherein, the added amount of carboxymethyl chitosan
is 50 kg and the added amount of dopamine hydrochloride is 5 kg,
but the added amount of acrylic acid is 35 kg. The measured
weight-average molecular weight of the reaction product GBFS-2 is
69,100 g/mol.
Example 3
[0068] Prepare a polymer GBFS-3 with the same method as that used
in example 1, wherein, the added amount of carboxymethyl chitosan
is 50 kg and the added amount of dopamine hydrochloride is 85 kg,
but the added amount of acrylic acid is 35 kg. The measured
weight-average molecular weight of the reaction product GBFS-3 is
93,250 g/mol.
Example 4
[0069] Prepare a polymer GBFS-4 with the same method as that used
in example 1, wherein, the added amount of carboxymethyl chitosan
is 50 kg and the added amount of acrylic acid is 50 kg, but the
added amount of dopamine hydrochloride is 2.5 kg. The measured
weight-average molecular weight of the reaction product GBFS-4 is
83,200 g/mol.
Example 5
[0070] Prepare a polymer GBFS-5 with the same method as that used
in example 1, wherein, the added amount of carboxymethyl chitosan
is 50 kg and the added amount of acrylic acid is 50 kg, but the
added amount of dopamine hydrochloride is 8 kg. The measured
weight-average molecular weight of the reaction product GBFS-5 is
85,380 g/mol.
Comparative Example 1
[0071] Prepare a dopamine-modified polyacrylic acid with the method
disclosed in the literature (J. Wu, L. Zhang, Y. Wang, et al.
Mussel-Inspired Chemistry for Robust and Surface-Modifiable
Multilayer Films[J]. Langmuir, 2011, 27(22): 13684-13691).
Comparative Example 2
[0072] Prepare a dopamine-modified polyethylene glycol with the
method disclosed in the literature (B. P. Lee, J. L. Dalsin, P. B.
Messersmith. Synthesis and Gelation of DOPA-Modified Poly(ethylene
glycol) Hydrogels[J]. Biomacromolecules, 2002, 3(5):
1038-1047).
Test Example 1
[0073] This test example is used to measure the wellbore
reinforcing effect.
[0074] Immerse shale debris in 3 wt % water solution of GBFS-1, and
observe the morphology change of the shale debris after 1 h and 3 h
respectively. The result is shown in FIG. 1. In initial state,
there is no other substance adhering to the surface of the shale
debris immersed in the pale brown clear solution of GBFS-1. After 1
h immersion, a straw yellow sticky substance begins to form on the
debris surface, and it glues adjacent small debris together. At
this point, the bulk phase solution is still clear. After 3 h
immersion, the coverage of the straw yellow sticky substance on the
debris surface has expanded, and the gluing effect is stronger. At
this point, the bulk phase solution away from the debris is still
in clear state. Thus, it is apparent that the GBFS-1 provided in
the present invention can effectively stabilize wellbore.
Test Example 2
[0075] This test example is used to measure the wellbore
reinforcing effect.
[0076] Heat shale debris by roll-heating in tap water in a roller
heater at 120.degree. C. for 16 h, and then take out the debris,
dry them, and observe the morphology of the debris. A SEM photo of
the morphology is provided in FIG. 2.
[0077] Heat shale debris by roll-heating in 3 wt % water solution
of GBFS-1 in a roller heater at 120.degree. C. for 16 h, and then
take out the debris, wash the debris surface with some clean water,
and dry the debris; then, observe the morphology change of the
shale debris. A SEM photo of the morphology is provided in FIG.
3.
[0078] It can be seen from the comparison between FIG. 2 and FIG.
3: 3 wt % GBFS-1 forms a layer of dense polymer coating on the
shale debris surface, and the pores of the debris are essentially
plugged off.
Test Example 3
[0079] This test example is used to measure the filter loss
reduction performance.
[0080] Add 3 wt % GBFS-1.about.GBFS-5, dopamine hydrochloride,
dopamine-modified polyacrylic acid, and dopamine-modified
polyethylene glycol into 4 wt % bentonite base slurry, stir at a
high speed for 20 min, and then age for 16 h at 120.degree. C. in a
roller heater, respectively. Then, take out and cool down them, and
measure the API filter loss with a medium-pressure filter press
(Model SD4, purchased from QingDaoTongchung Oil Instrument Co.,
Ltd.), respectively. The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Sample API Filter Loss/mL 4 wt % bentonite
slurry 29 GBFS-1 11 GBFS-2 15 GBFS-3 8.5 GBFS-4 12 GBFS-5 15
Dopamine hydrochloride 276 Dopamine-modified 11 polyacrylic acid
Dopamine-modified 13 polyethylene glycol
Test Example 4
[0081] This test example is used to measure the lap shear
strength.
[0082] Bond two shale core samples (length: 12.5.+-.0.5 mm,
thickness: 2.0.+-.0.1) by butt jointing with GBFS-1.about.GBF S-5,
dopamine hydrochloride, dopamine-modified polyacrylic acid,
dopamine-modified polyethylene glycol, polyvinyl acetate, ethyl
cyanoacrylate, and epoxy resin in dry environment and water
environment, respectively, and then apply longitudinal shearing
force in opposite directions on the two samples bonded together by
a servo tension tester, and measure the shearing force when the two
shale core samples are separated from each other. The value of the
shearing force is the lap shear strength. The results are shown in
Table 2. The amount of the materials described above is the same
for each test.
TABLE-US-00002 TABLE 2 Lap Shear Strength (MPa) Gluing in Dry
Gluing in Water Sample Environment Environment GBFS-1 3.8 .+-. 0.5
0.18 .+-. 0.04 Polyvinyl acetate 4 .+-. 1 .apprxeq.0 Ethyl
cyanoacrylate 7 .+-. 1 .apprxeq.0 Epoxy resin 11 .+-. 2 0.07 .+-.
0.03 GBFS-2 3.1 .+-. 0.3 0.12 .+-. 0.03 GBFS-3 3.8 .+-. 0.2 0.18
.+-. 0.02 GBFS-4 3.4 .+-. 0.3 0.16 .+-. 0.03 GBFS-5 3.5 .+-. 0.5
0.16 .+-. 0.04 Dopamine hydrochloride 0 0 Dopamine-modified 1.2
.+-. 0.6 .apprxeq.0 polyacrylic acid Dopamine-modified 2.1 .+-. 0.3
0.09 .+-. 0.03 polyethylene glycol
Test Example 5
[0083] This test example is used to measure the shale core
strength.
[0084] Obtain ten shale cores that have essentially the same
properties, immerse nine of them in tap water, 3 wt % water
solution of GBFS-1, 3 wt % water solution of GBFS-2, 3 wt % water
solution of GBFS-3, 3 wt % water solution of GBFS-4, 3 wt % water
solution of GBFS-5, 3 wt % water solution of dopamine
hydrochloride, 3 wt % water solution of dopamine-modified
polyacrylic acid, and 3 wt % water solution of dopamine-modified
polyethylene glycol respectively; and then heat them by
roll-heating at 120.degree. C. for 16 h respectively. Leave the
remaining shale core being untreated.
[0085] Take out the roll-heated shale cores, and immediately carry
out uniaxial breaking test for them by a uniaxial compressive
strength tester respectively, to evaluate the effect of the
wellbore reinforcers to shale core strength. The results are shown
in Table 3.
TABLE-US-00003 TABLE 3 Breaking Length, Diameter, Weight, Density,
Strength, Shale Core Sample mm mm g g/cm.sup.3 MPa Blank shale core
78.5 25.2 69.34 1.78 6.91 sample water 79.5 25.0 70.14 1.79 0.01
GBFS-1 77.3 24.8 66.84 1.79 5.96 GBFS-2 77.2 25.0 66.38 1.75 5.00
GBFS-3 77.8 25.4 69.34 1.76 6.20 GBFS-4 77.2 25.2 67.34 1.75 5.52
GBFS-5 78.3 25.4 70.59 1.78 5.32 Dopamine 78.2 25.0 67.71 1.76 0.01
hydrochloride Dopamine-modified 76.6 25.2 66.55 1.79 2.31
polyacrylic acid Dopaimne-modified 77.6 24.8 67.06 1.79 4.89
polyethylene glycol
Test Example 6
[0086] This test example is used to measure the percentage recovery
of shale after roll-heated in sample solutions for 16 h.
[0087] Immerse approximately 30 g 6-10 meshes shale debris in 300
mL tap water, 3 wt % water solution of GBFS-1, 3 wt % water
solution of GBFS-2, 3 wt % water solution of GBFS-3, 3 wt % water
solution of GBFS-4, 3 wt % water solution of GBFS-5, 3 wt % water
solution of dopamine hydrochloride, 3 wt % water solution of
dopamine-modified polyacrylic acid, and 3 wt % water solution of
dopamine-modified polyethylene glycol respectively; and then heat
them by roll-heating at 120.degree. C. for 16 h, and filter with a
40 meshes screen, and dry the debris left on the screen at
120.degree. C. till the weight doesn't change any more. The ratio
of this weight to the original weight of the shale debris is the
percentage recovery. The results are shown in Table 4.
TABLE-US-00004 TABLE 4 Sample Percentage recovery/% Tap water 43.09
GBFS-1 93.17 GBFS-2 85.78 GBFS-3 97.42 GBFS-4 90.33 GBFS-5 88.17
Dopamine hydrochloride 83.80 Dopamine-modified 81.59 polyacrylic
acid Dopamine-modified 65.48 polyethylene glycol
[0088] While some preferred embodiments of the present invention
are described above, the present invention is not limited to the
details in those embodiments. The person skilled in the art can
make modifications and variations to the technical scheme of the
present invention, without departing from the spirit of the present
invention. However, all these modifications and variations shall be
deemed as falling into the protected scope of the present
invention.
[0089] In addition, it should be noted: the specific technical
features described in above embodiments can be combined in any
appropriate form, provided that there is no conflict. To avoid
unnecessary repetition, the possible combinations are not described
specifically in the present invention.
[0090] Moreover, different embodiments of the present invention can
be combined freely as required, as long as the combinations don't
deviate from the ideal and spirit of the present invention.
However, such combinations shall also be deemed as falling into the
scope disclosed in the present invention.
* * * * *